The present application claims priority from and the benefit of Japanese Patent Application No. 096020/2001, filed Mar. 29, 2001.
1. Field of the Invention
The present invention relates to an ophthalmologic apparatus which allows easy alignment of a measurement optical system with respect to a patient""s eye to be examined, and an auto-alignment method for the apparatus.
2. Related Background Art
An ophthalmologic apparatus having an auto-alignment function is known.
Such an ophthalmologic apparatus can perform so-called auto-alignment, in which a light beam is projected on the cornea of an eye to be examined, and the alignment state of the optical axis of the measurement optical system with respect to the eye is detected by detecting the reflected light through a light-receiving element, thereby automatically setting the relation between the eye and the optical axis of the measurement optical system to have a predetermined relationship on the basis of the alignment state.
The above auto-alignment function exhibits a narrow range in which reflected light from the cornea can be detected by the light-receiving element; there is a room for improvement.
When the measurement optical system in the initial state falls outside a detectable range in which auto-alignment can be done, and no reflected light can be detected, an operator needs to manually align the measurement optical system (measurement unit) with the eye until the optical system falls within the detectable range.
Such operation is a burden for the operator of this apparatus, and hinders quick measurement. One of measures against this problem is to widen the detectable range of alignment by using a large-aperture light-receiving lens or a sensor having a large light-receiving surface. An increase in apparatus size, however, will lead to increases in cost and complexity.
According to another approach, the ophthalmologic apparatus disclosed in Japanese Patent Application Laid-Open No. 9-66027 is aimed at widening the detectable ranges in the up-and-down and right-and-left (X and Y) directions by performing alignment detection on the basis of a virtual image of an anterior illumination light source on an eye to be examined. However, since no special optical system for alignment detection is used, high detection precision cannot be ensured. In addition, according to the structure of this apparatus, the detectable range for alignment in the forward-and-backward (Z) direction cannot be broadened.
It is an object of the present invention to provide a method and ophthalmologic apparatus which allow high-precision auto-alignment in a wide range.
In order to achieve the above object, according to an aspect of the present invention, there is provided an ophthalmologic apparatus comprising a movable measurement unit which includes a measurement optical system for measuring an eye to be examined, a first light source which irradiates the eye with light from a direction different from an optical axis of the measurement optical system, a second light source which irradiates the eye with light from an optical axis direction of the measurement optical system, an image pickup device to obtain an image of the eye, a first detection system which detects an aligned state of the measurement unit with the eye by obtaining a position of a reflected cornea image of the second light source on the basis of the image picked up by the image pickup device, and a second detection system which detects an aligned state of the measurement unit with the eye by detecting a position of the reflected cornea image of the first light source on the basis of the image picked up by the image pickup device.
According to another aspect of the present invention, there is provided an auto-alignment method for an ophthalmologic apparatus including a measurement optical system which measures an eye to be examined, and an illumination system which illuminates the eye with extrinsic eye light, comprising the detection step of irradiating the eye with a light beam through the measurement optical system, and detecting a reflected cornea image of the light beam, the aligning step of, when a reflected cornea image can be detected in the detection step, aligning the measurement optical system with the eye on the basis of a position determined based on the reflected cornea image, and the step of, when no reflected cornea image can be detected in the detection step, detecting a reflected cornea image by illumination of the extrinsic eye light, aligning the measurement optical system in accordance with the detected reflected cornea image, and then performing the detection step again.
The above and other objects, features, and advantages of the present invention will be apparent from the following detailed description in conjunction with the accompanying drawings and the appended claims.